The present invention relates to blocks or stacks of interleaved laminar products of the kind disclosed for example, in EP-A-0 955 260 and European Patent Application 99830650.0.
Various requirements must be met in the forming of stacks of interleaved laminar products of this type, which usually consist of personal hygiene products such as handkerchiefs, napkins, including pre-moistened products (known as xe2x80x9cwet wipesxe2x80x9d or xe2x80x9cmoist tissuesxe2x80x9d), toilet paper, etc.
In the first place, it is important to ensure that the interlacing (interleaving) relationship between the products in the stack is such that the correct execution of the operation of withdrawing the individual products from the stack is ensured. In particular, it is necessary to ensure that the movement of the withdrawal of a product (particularly through a slot or hole in the box or envelope used as the package for the stack) causes the automatic and correct preparation of the immediately following product for withdrawal. The whole procedure must prevent the following product from being at least partially withdrawn from the package in an undesired way.
In this connection it must be borne in mind that the determination of the interleaving relationship between successive products in the stack is subject to various factors such as:
the characteristics of the material from which the products are made (paper, textile or non-woven materials, etc.),
the possible presence of agents for pre-moistening the products, and, in the latter case,
the specific characteristics (degree of adhesiveness/slip, etc.) of the substances used as agents for impregnating the material which is to be pre-moistened.
Furthermore, it is necessary to bear in mind other factors such as the requirement to minimize the surface of the product which remains exposed at the end of the stack facing the exterior, in other words at the end facing the withdrawal aperture: the portion of product exposed to the exterior can, in the case of pre-moistened products, lose at least some of its pre-moistening characteristics over a period of time, and, even in the case of non-pre-moistened products, becomes exposed, to a certain extent at least, to phenomena of contamination by external agents.
Certain interleaving methods proposed in the prior art are also subject to a drawback due to the fact that the stack of interleaved products has a different number of overlapping layers in different parts of its cross-sectional profile. The stack can thus finally assume a shape different from the right-angled parallelepiped which is usually preferred, taking on a swollen configuration at one or both of its sides or in its central portion. The described phenomenon is not essentially different from the phenomenon generally known as xe2x80x9crisingxe2x80x9d which occurs during the stacking of signatures in the printing industry, where, however, the phenomenon is essentially due to the presence of the spine folds of the signatures, rather than to the different number of overlapping layers.
Other factors to be borne in mind may be mentioned, such as the requirement to ensure that the interleaving process can be implemented simply and efficiently, without undesired complications, and the fact that the stack of interleaved products should preferably be symmetrical, and thus be such that it does not have a preferred direction of orientation for the purposes of insertion into a package, particularly when the package is to be provided with an aperture or slot for withdrawal of the products.
It is also important to ensure that the part of each product designed to act as the pick-up flap for the product is located in a central position, or in any case in a specified position. In this connection, there are documents such as U.S. Pat. No. 3,401,927, relating to special folding solutions intended to ensure that the pick-up flap of the first product is positioned next to the pick-up slot of the package.
The object of the present invention is to provide a solution capable of meeting the requirements expressed above while also avoiding the drawbacks described previously.
According to the present invention, this object is achieved by means of a stack of interleaved products having the characteristics claimed in the following claims.
The invention also relates to the corresponding package and the corresponding forming process.
The solution according to the invention not only meets the aforesaid requirements and avoids the drawbacks described previously, but has further advantages such as, for example, the advantage due to the possibility of varying the interleaving relationship between the products in a selective way without causing a variation in the overall width of the stack. This characteristic is particularly advantageous since, for example, it makes it possible to use packages of identical dimensions for containing stacks of interleaved products with different characteristics. In addition to this, the solution according to the invention makes it possible to provide the desired central positioning of the pick-up flap of the products.